To get started with Jython you need two things, Java and Jython itself. First, you need to get a Java Runtime Environment* (JRE). Any environment that is based on at least JDK 1.1 will work; this includes all versions of the Java 2 Platform. Both Microsoft's non-standard version that previously shipped with Visual J++* and IBM's Developer Kit for Windows* will work fine. This also means that Jython programs will run fine in Internet Explorer* and Netscape* browsers without using the Java plug-in.

Once you have a JRE, you can install Jython. Get the latest version, 2.1 as of the time of this writing, from SourceForge. Jython comes as a single .class file that is actually an installable program. Save the class file (jython-21.class) to the directory locally. Once saved, run the class to start the installer. If the current directory is in your classpath, just run it as follows:

    java jython-21

If the current directory is not in your classpath, you'll need to include it:

    java -classpath . jython-21 or java -cp . jython-21

The installation window displays.


Figure 1. Jython Installation Window.

You'll be prompted for various options including installation type (pick at least Standard) and directory (we'll assume C:\jython-2.1 for the purpose of this article). On the final installation screen click the Go button and you'll be all set.

After the installation is complete, place the installation directory in your path. With C:\jython-2.1 in your path, you'll be able to just type jython to launch the interactive console. You're now ready to get started with Jython.

The typical first program in any language is called "Hello, World." It just prints out a little message. Here, we'll print out "Hello, Jython" instead. To start the console, type jython. The first time you launch Jython, some processing will happen of preinstalled libraries for your JRE. After the first time, it won't be necessary again. Once Jython loads, you get a >>> prompt.

The equivalent to a System.out.println call in Python is just print. So, if you want to print a message to the console, follow the command with a quoted string, as shown here. The string is immediately displayed since the console is interactive, interpreting each command as it is entered.

     >>>print "Hello, Jython"



    Hello, Jython

Exit the environment with Ctrl-Z.

If you're not interested in typing the command each time, you can save it to a file:

     # file hello.py





    print "Hello, Jython"

Launch Jython with the filename, as shown here:

    jython hello.py